Method for detecting security error in mobile telecommunications system and device of mobile telecommunications

1. A method of performing a re-establishment procedure in a mobile communication system, the method comprising:

receiving at least one packet data convergence protocol (PDCP) control plane data unit;

performing an integrity check on the at least one PDCP control plane data unit;

identifying an integrity check failure with regard to the at least one PDCP control plane data unit; and

performing a re-establishment procedure if the integrity check failure is identified to exist with regard to the at least one PDCP control plane data unit.

2. The method of claim 1 , wherein the re-establishment procedure comprises at least re-establishing a radio bearer (RB) or re-establishing a radio resource control (RRC) connection.

3. The method of claim 1 , wherein performing the integrity check on the at least one PDCP control plane data unit comprises:

counting a number of integrity-failed PDCP control plane data units among the at least one PDCP control plane data unit received; and

comparing the number of integrity-failed PDCP control plane data units counted to a reference value,

wherein the integrity check failure is identified if the number of integrity-failed PDCP control plane data units counted reaches the reference value.

4. The method of claim 3 , wherein the integrity-failed PDCP control plane data units are in a consecutive order.

5. The method of claim 1 , wherein the integrity check failure is identified if a message authentication code-integrity (MAC-I) value of the at least one PDCP control plane data unit received is different from an expected message authentication code-integrity (XMAC-I) value.

6. The method of claim 1 , further comprising:

deciphering the at least one PDCP control plane data unit received.

7. The method of claim 6 , further comprising:

removing at least one PDCP header from the at least one PDCP control plane data unit received.